Connecting the dots on aerosol details

July 27, 2011

Pollution aerosols and their effect on the Earth’s energy budget are part of the picture that climate scientists are focusing on in multi-scale climate modeling.

Predicting future climate change hangs on understanding aerosols, considered the fine details in the atmosphere. Researchers at Pacific Northwest National Laboratory and the National Center for Atmospheric Research used a new modeling tool to bring the picture of aerosols and their actions on clouds into sharper focus.

The multi-scale aerosol-climate model, an extension of a multi-scale modeling framework, examined specific aerosol-cloud interactions and their effects on the Earth's energy budget, one of the toughest climate forecasting problems. Their results show that the cooling effect of human-caused atmospheric aerosols is smaller than previously thought.

Current global climate models used to predict climate change account for large-scale climate processes, typically at scales greater than 100 kilometers, or about 62 miles. This means small-scale and regional features in the climate tend to be averaged out, or estimated through parameterization, a technique used to represent complex small-scale systems. Because small-scale climate features, such as clouds and atmospheric aerosol particles, have a large impact on global climate, it's important to improve the methods used to represent those climate features in the models. This study has advanced scientists' capabilities to model and predict those complex aerosol-cloud interactions on the Earth's energy budget, for a balanced and energy-sustainable future.

Scientists at PNNL developed a new aerosol-climate model as an extension of a multi-scale modeling framework model that embeds a cloud-resolving model (CRM) within each grid column of a global climate model. This model, called the PNNL-Multi-scale Modeling Framework, depicts aerosol-cloud interactions in both stratiform and convective clouds in a more realistic way than conventional global models. In addition, the PNNL-MMF is much more computationally feasible for running multi-year climate simulations than a global CRM.

The cloud response to aerosols shows only one-third as strong as it did in previous modeling in the study using the PNNL-MMF. Scatter plots show changes in liquid water path response (LWP) versus cloud condensation nuclei (CCN) perturbation from anthropogenic aerosols in a) MMF (new model), and b) CAM5 (previous model). Anthropogenic, or human-caused aerosols are primarily the result of fossil fuel burning.

The team evaluated simulated cloud fields from the multi-scale aerosol-climate model and examined how specific human-caused aerosols, such as sulfate, black carbon (soot), and organic carbon affect those clouds and, in turn, the climate. The PNNL-MMF is a more physically based way to represent the indirect effects of aerosols compared to parameterization, typically used to represent small-scale climate details in global models. The significant computational resources available to the team at the National Center for Computational Sciences at Oak Ridge National Laboratory enabled this improvement in climate modeling.

The study compared pre-industrial and present-day results in current global models to the newer high-resolution model with the PNNL-MMF extension. Comparisons show a lesser effect on the Earth's energy budget, considering the additional burden of human-caused aerosols. These results confirm the need to use global high resolution models to study the aerosol indirect effects.

The researchers are working to understand the differences found between global models and the more detailed PNNL-MMF results. In future work, the team will tackle the aerosol effects on precipitation.

Related Stories

As climate change scientists develop ever more sophisticated climate models to project an expected path of temperature change, it is becoming increasingly important to include the effects of aerosols on clouds, according ...

A group of scientists affiliated with the International Geosphere-Biosphere Programme (IGBP) have proposed a new framework to account more accurately for the effects of aerosols on precipitation in climate models. Their work ...

Scientists need a more detailed understanding of how human-produced atmospheric particles, called aerosols, affect climate in order to produce better predictions of Earth's future climate, according to a NASA-led report issued ...

The devil is in the details, the very small details, when it comes to global climate models, and those details are now easier to see, thanks to climate change researchers from Pacific Northwest National Laboratory. The team ...

For the first time, researchers have developed a comprehensive approach to look at aerosolsthose fine particles found in pollutionand their effect on clouds and climate. Scientists from Pacific Northwest National ...

Atmospheric aerosols may be small, ranging in size from a few nanometers to a few microns, but they have a big impact on climate. At the Pacific Northwest National Laboratory, capabilities developed through the Laboratory ...

Recommended for you

At the end of the Pleistocene period, approximately 12,800 years ago—give or take a few centuries—a cosmic impact triggered an abrupt cooling episode that earth scientists refer to as the Younger Dryas.

In a new assessment of nine state-of-the-art climate model simulations provided by major international modeling centers, Michael Rawlins at the University of Massachusetts Amherst and colleagues found broad disagreement in ...

New research confirms that the land under the Chesapeake Bay is sinking rapidly and projects that Washington, D.C., could drop by six or more inches in the next century—adding to the problems of sea-level rise.

The world's deserts may be storing some of the climate-changing carbon dioxide emitted by human activities, a new study suggests. Massive aquifers underneath deserts could hold more carbon than all the plants on land, according ...

Wildfires in California's fabled Sierra Nevada mountain range are increasingly burning high-elevation forests, which historically have seldom burned, reports a team of researchers led by the John Muir Institute of the Environment ...

The paper demonstrated that the aerosol cooling effects in current climate models is over-estimated and that their model of lower cooling effects from human created aerosols better matches observations.From the Abstract "The smaller response in LWP to anthropogenic aerosols in the MMF model is consistent with observations..... "The simulated total anthropogenic aerosol effect in the MMF is -1.05 W m-2, which is close to the Murphy et al. (2009) inverse estimate of -1.1±0.4 W m-2 (1s) based on the examination of the Earth's energy balance."

NotParker, they may be guesses, but they're better guesses than you or I could make. I think this is good science, equitably reported, and should be supported by us scientists.A lot of work has gone into them and a lot of our tax money has been spent to arrive at where we are now.Let's at least try to get some of our money's worth out of all this research investment. Being dismissive of good work is not the way to do that.

They should add to the list of aerosols under study barium and aluminum oxides, which are probably the main components of the mid-level schmutz that can be seen as a thin haze at about 10,000 feet (?)_on a clear day.

Please sign in to add a comment.
Registration is free, and takes less than a minute.
Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.